Abstract - This review presents a broad overview of chorionic
glycoproteins encoded by the Pregnancy-Associated
Glycoprotein (PAG) gene family and also serves to illustrate how
the recent discovery of the PAG family has contributed to our general
knowledge of genome evolution, placental transcription and placental protein
expression. The complex and large PAG family is restricted to the
Artiodactyla order, although single PAG-like genes have also been identified in species
outside the Artiodactyla. The PAGs are members of the aspartic proteinase (AP)
superfamily. Unexpectedly, however, some members of the PAG family possess
amino acid substitutions within and around the active site that likely
render them unable to act as proteinases. This paper summarises the
available information regarding biodiversity of PAG gene expression based on
cDNA cloning, mRNA localisation studies and the structural organisation of
the PAG genes with a particular emphasis on PAG promoters. It also compares
available data regarding PAG protein purifications, sequencing and their
N-glycodiversity. Finally, it discusses the scientific relevance, possible
functional roles of the PAGs and describes possible profitable applications
related to the detection of PAG proteins in the blood of pregnant domestic
and wild species.